As is summarized in U.S. Pat. No. 4,055,191, the proportion of polycyclic aromatic hydrocarbons (PCAH) in the smoke from tobacco can be materially reduced by incorporating palladium into the tobacco. It is further disclosed that palladium in combination with a nitrate salt, preferably magnesium nitrate, is even more efficient in reducing PCAH. Moreover, the combination of palladium and nitrate was shown in tests on mice to materially reduce the biological activity of tobacco smoke condensate obtained by smoking cigarettes on a wheel-type smoker as described in